1. Field of the Invention
This invention pertains to automatic high-speed self-adhesive labeling machines. More particularly, the present invention relates to automatic high-speed labeling machines for labeling cylindrical containers which are linearly fed through the machine in a straight line, but are caused to rotate about their vertical axes through three points of contact with a powered rotating belt (or wheel or drum) and two passive rollers held at the apex of a freely rotating star wheel which results in the transfer of at least one label to a container and thereby causing the container to wrap the label around itself.
2. Description of the Prior Art
The prior art is replete with descriptions of labeling machines for cylindrical containers which all accomplish the same purpose but by different means.
For example, in U.S. Pat. No. 4,714,515 (1987), Hoffman describes a “straight line” container labeling apparatus including oppositely moving main drive and porous labeling belts, and a timing star and second star wheel having rollers on the ends of its arms for engaging and aligning each container while allowing it to rotate freely between the belts. In this apparatus, the leading edge of a continuous strip of label stock is gripped by a radially retracted vacuum pad located on the periphery of a rotating vacuum drum and pulled until a cutting knife carried directly on the drum severs the trailing edge of each label. The retracted vacuum pads are selectively extendable for application of adhesive and then may be retracted to allow fingers to strip each gummed label from the drum and transfer it to a vacuum wheel over which is entrained a porous labeling belt that carries each label to a container driven by the drive belt and aligned by the second star. Although workable in theory, this fairly complex labeling apparatus obviously required critical synchronization of its interrelated elements to function properly. During high speed labeling operations (more than 125 containers per minute) several problems arose. For example, containers would often jam as they left the timing star and became wedged by an arm of the aligning star. Additionally, the reciprocating vacuum pads on the vacuum drum did not provide a uniform glue pattern on the labels which often caused glue to be deposited on the porous labeling belt resulting in labels stuck thereon. Moreover, part of the cutting means was located on the periphery of the vacuum drum which, of course, increased in rotational speed with the speed of the labeling operation, and often resulted in improperly cut labels. Thus, the labeling apparatus as above described was short lived in actual high speed production and is not known to be in use today. This method disclosed a star wheel with small rollers (bearings) only at the top and/or at the bottom of the container to assist in the stability and the guiding the containers but this star wheel is powered by the system and is continuously rotating by necessity as this is a continuous motion machine, hence is a complex and expensive system.
In U.S. Pat. No. 4,931,122 (1990), Mitchell discloses another straight through labeling machine with a “feed-screw” for moving cylindrical containers past, but in tangent to, a vacuum drum containing precut gummed labels. The containers travel along a guide-way to the feed screw where they also contact an endless belt causing the containers to spin counter-clockwise around their vertical axes. As the feed screw advances the containers linearly past, but in tangent to, the vacuum drum, a label is transferred to a container and is preferably wrapped around it before said container exits the feed screw. Although this labeling machine appears to be an improvement over the cited prior art, the counter-clockwise rotation of the containers while being linearly advanced within the feed screw causes vertical drag or a retarding force acting on the containers due to friction which is undesirable in high speed labeling operations. Although the feed screw has the effect of aligning the containers vertically, the alignment is only between the root of the screw and the rotating drum, which alignment is improved only by constraining the containers more and more which has adverse effect of jamming the labels as the constraints are tightened.
In U.S. Pat. No. 4,428,474 issued on Jan. 31, 1984 to Gau, et al., disclose an apparatus for aligning containers in a labeling machine. The apparatus comprises pairs of moveable arms, adjacent container pockets on a star wheel, and a belt carried on the arms. The belt is rotated by a motor which, in turn, causes a container in the star wheel pocket to rotate. A sensor detects marks on the containers and applies a brake to stop rotation of the belts, thereby locking the containers in a pre-determined angular orientation. While this would rotate containers and stop them at an appropriate position for labeling with respect to a witness mark on the container, the system is complex and expensive.
Aesus literature Premier wrap 20060621 discloses a system of rollers which index forwards and backwards, while capturing containers against a rotating wrap belt into a position to appropriately apply a pressure sensitive label. This system adequately grips the container, holds it correctly in a vertical axis, allows time for the container to rotate (if required) to a location where the label should be applied relative to a witness mark (seam, spot, or other witness mark) and then signals the label head to dispense the label (or labels) while the container continues to be rotated and held aligned in the vertical axis. Although the system works well, it is limited in speeds to approximately 50 containers per minute.
Aesus literature Premier star wrap 20080122 describes a system of a continuously rotating star wheel that has rollers at the apex of the star wheel which hold the container against a wrap belt similarly, with the whole system being driven by servomotors that are synchronized in order to position the container at the precise point where label needs to be applied. This system works at speeds greater than 50 containers a minute even to speeds in excess of 300 containers per minute, but the combination of servomotors and precise controls making a costly and unaffordable solution for many labeling applications, and it does not have the capability of applying more that one sequential label (ie: separate front and back labels) to each container as the container is continuously moving away from the label dispensing apparatus.